The Syntax and Semantics of the Scheme Programming Language

For example, the syntax rules of the English language tell us that person, tall, told, the, a, me and joke are legal words, and that The tall person told me a joke is a legal sentence, whereas pkrs, shrel and fdadfa are not legal words, and Person tall told a me the is not a legal sentence. The semantic rules tell us what each of the words mean (e.g., what objects the nouns denote and what processes the verbs convey), as well as what the entire sentence means (i.e., that a particular tall person told me a joke). For another example, the syntax rules of French tell us that je, vais, au, tableau and noir are legal words, and that Je vais au tableau noir is a legal sentence; and the semantic rules tell us that this sentence means that I am going to the blackboard. In a similar way, people use a programming language to communicate with a computer. And each programming language has an associated set of syntax rules that specify the legal expressions (or statements or sentences or programs) that can be used in that language, and a set of semantic rules that specify what the legal expressions mean (i.e., what computations the computer will perform). For most computer programming languages, the constituents of the langage, whether they are called expressions, statements or entire programs, are usually sequences of typewritten characters. For example, the following character sequences are legal building blocks of a Java program: